Originally Posted by
JohnDThompson
There were actually several versions of the keyed washer, depending on what dropout you were using: one for the Huret-type dropouts, one for the unthreaded Simplex dropouts, and one for the Campy type dropouts.
I'll have to see if I can find some without removing a derailleur from one of the bikes.
Ok, here's a couple pictures of the Huret tabbed washers. These were not unique to the Duopar derailleurs, so if you can find a cheap/mangled Challenger or Success derailleur you can salvage the hardware for them to get your Duopar up and running. The old "Alvit" and "Svelto" units also used a tabbed washer but generally came on the Huret-type mounting claw and won't directly work on a Campy type dropout.
Here's the Huret-type claw and hardware on the top row and Campy-type mounting hardware on the bottom row:
Here's a close-up of the tabbed washer:
Note that in addition to the bent tab designed to catch the stop on the dropout, there are also a pair of punched indents in the washer to fit into a slot on the derailleur to hold it in place. You
can get by with a simple flat washer if you crank the mounting bolt down hard to prevent the derailleur from pivoting on the mounting bolt, but that complicates wheel removal and is less than ideal.